Best way to implement user-dependent validations

rubyonrails-talk
,
1

Say the users of my app are admins of email domains and each of them is allowed to create mailboxes for one or multiple domains by typing out the email address for that mailbox. Currently, the Mailbox-model has an unpersisted attribute that acts as a whitelist for domains.

Is there an alternative/better way to implement something like this? I most likely want to implement this as a model validation to display a nice message to the user. I do not want to discard invalid email attributes nor do I want to have a view-only solution (something like using a <select> for the domain).

class Mailbox < ApplicationRecord
  attribute :_allowed_domains, array: true

  validates :email, presence: true, format: URI::MailTo::EMAIL_REGEXP
  validate :email_domain_allowed, if: :email

  private
  def email_domain_allowed
    raise "_allowed_domains is not populated, cannot validate" if self._allowed_domains.nil?

    self.errors.add(:email, :domain_not_allowed) if self._allowed_domains.exclude?(self.email.split("@", 2).last)
  end
end

class MailboxesController < ApplicationController
  def create
    @mailbox = Mailbox.new(mailbox_params)
    respond_to do |format|
      if @mailbox.save
        format.html { redirect_to(@mailbox) }
        format.json { head(:created) }
      else
        format.html { render("new", status: :unprocessable_content) }
        format.json { render(json: { error: @mailbox.errors.full_messages.to_sentence }, status: :unprocessable_content) }
      end
    end
  end

  private
  def mailbox_params
    parameters = params.expect(mailbox: [:email])
    parameters[:_allowed_domains] = current_login.user.allowed_domains
    return parameters
  end
end